Numerical Analysis of Free Molecule Micro-Resistojet Performance

摘要

One of the most crucial requirements of modern space missions is the miniaturization of spacecraft and satellites. The miniaturization is tightly connected with new space technologies promoted by the Air Force, DARPA, and NASA, such as spacecraft formation flying, that implies two or more spacecraft that operate synchronously in a controlled spatial configuration. This, in turn, necessitates the development of new propulsion systems able to deliver precise impulse bits while meeting strict mass, size and power usage limitations. Currently, various micropropulsion concepts are being considered, such as cold gas; catalytic decomposition; mono- and bi-propellant; and thrusters. For most micropropulsion devices, the fluid mechanics of reduced length scales (low Reynolds numbers) dictates that there will be a significant degradation of the thrust efficiency due to increased viscous and heat transfer losses. Both experimental and numerical investigation of fluid flow and performance of microthrusters is necessary for realistic evaluation of advantages and drawbacks of the new micropropulsion concepts. In this work, a Free Molecule Micro-Resistojet (FMMR) is examined numerically, that was developed and described in Ref.,4 and recently studied experimentally in Ref.5 The FMMR is an electrothermal propulsion system designed for on-orbit maneuvers of nanospacecraft (mass 10 kg). The FMMR is being developed to fly on a Texas A AND M (TAM)nanosatellite. This nanosatellite flight will investigate the survivability and capability of water propelled micro-thrusters for attitude control maneuvers on a small satellite and could also mark the first operation of a MEMS fabricated thruster in space. The delivered thruster system will operate on the vapor pressure of water, stored in either a liquid or solid state (depending on the internal satellite temperature). The FMMR will provide a de-spin capability for the nanosatellite to allow positioning of the satellite.